Stability Analysis of Single-Loop Voltage Magnitude Controlled Grid-Forming Converters Considering Voltage Loop Parameter Impact

With the large-scale integration of renewable energy generation systems, the voltage support capability at the point of common coupling (PCC) has become increasingly insufficient. Against this background, grid-forming voltage source converters (GFM-VSCs), which provide frequency and voltage support, have attracted widespread attention. Although such systems offer superior controllability and operational flexibility, they are prone to synchronous frequency resonance (SFR) issues, which are particularly evident under single-loop voltage magnitude (SLVM) control. This study establishes a sequence impedance model of GFM-VSC under single-loop voltage magnitude control and reveals its stability characteristics through pole-zero analysis. The results demonstrate that the proportional gain in the voltage loop introduces a negative damping effect on synchronous oscillations, while the impact of the integral gain is relatively minor. Furthermore, excessive droop coefficients, excessively high cutoff frequencies of the low-pass filter (LPF), and insufficient line damping can all trigger SFR, especially under weak grid conditions.